Going on a cruise is definitely different. Our first two were four nights on the Disney Dream (love that ship). I wouldn't worry about not going with more people. This could be a very special mother/daughter time. There are open houses when you first get on board for the kids clubs, so you can both check it out to see if your daughter would like it. Like others mentioned, there are classes/activities to go to, also. The restaurants and food options are super! When you know your itinerary, you can have fun searching the for shore excursions you'd like to do. One year at Nassau, we did the submarine tour (it wasn't that great). The next time we were there, we did the Dolphin Encounter. That was awesome!! For
Castaway Cay, we rented bikes and explored the island, swam with the stingrays and enoyed the beach. Next January we're going to be trying a 6 night cruise on Disney Wonder. We're looking forward to a longer trip this time. Hope everything works out for you!